From Greek Leonidas, meaning "lion-like" or "son of the lion."
Leonid is the Slavic and Eastern European form of Leonidas, the ancient Greek name meaning "son of a lion" — from λέων (leon, lion) plus the suffix denoting lineage. The original Leonidas is most famously immortalized in history as the Spartan king who led three hundred warriors at the Battle of Thermopylae in 480 BCE, holding the mountain pass against the Persian army of Xerxes in one of antiquity's most celebrated last stands. That story of heroic sacrifice gave the name a permanent heroic resonance in Western consciousness.
In its Russian and Ukrainian form, Leonid became widely used through the nineteenth and twentieth centuries. The Soviet leader Leonid Brezhnev (1906–1982), who presided over the USSR for eighteen years, is perhaps the best-known modern bearer, though the name also belongs to Leonid Kantorovich, the Soviet mathematician who won the 1975 Nobel Prize in Economics, and Leonid Andreyev, the influential symbolist writer of the early twentieth century. In science, the annual Leonid meteor shower — peaking each November — takes its name from the constellation Leo, connecting the name to one of the year's most spectacular celestial events.
Outside Russia and Eastern Europe, Leonid is rare, which gives it an air of distinction and cultured internationalism. It has attracted occasional use among parents who admire its powerful sound — the rolling 'L,' the hard stop of 'd' — and its layered heritage spanning Greek legend, Slavic culture, and the cosmos itself.